Books:

Books form  one of the primary sources of information. They provide a cohesively organised (thought content) information on a specific subject of optimum depth. Since book writing, editing, processing and publishing call for a considerable amount of time, books can be said to contain  ideas which are fairly well established. They form useful repositories of information both for teachers and learners in a particular field as they contain a  crystallised presentation of ideas helpful  to the majority of readers. 

A book is a physically independent document as  distinguished from  a periodical publication, that is, it has been completed in a definite number of volumes. A book normally deals with a subject of great extension and less intension. It is thus a macro- document. As per the norms prescribed by UNESCO, a book should have at least 49 pages, 22 to 32 cm. height, and 1.5 to 4 cm. thickness.  

A book may be a single-volume or multi-volume document. It may be a general document or a textbook or a reference book 

Single-volumed book: A book maybe in a single volume or in more than one volume. The latter is known as a multi volumed book. A multi-volumed book usually has a common index. It also  has the same sequence of pagination continued in all the volumes of the set. 

Simple book and Composite book: A book, either by a single author or by two or more authors., that gives a continuous exposition of the subject, is known as a simple book. A book by more than one author, all contributions of which do not form a continuous exposition but have one title distinct and independent, is a composite bock If a composite book has a single generic title to denote all the contributions collectively, it is an ordinary composite book, otherwise it is an artificial composite book. 

General book, Reference book and Textbook: A book is either a general book, a text-book or a reference book. A general book deals with the subject in a general way. A book giving general exposition on the subject, or a biography, or a fiction is a general book. Examples of general books are: Ranganathan's Five Laws of Library Science, Girja Kumar's Philosophy of User Education, Dhyaneshwar's Gita: the Mother. 

A textbook is one that supports a teaching programme. It deals with the fundamentals of the subject using the language and style that suits the students. An author's newly propounded theory is usually not found in it. Different courses of study have different textbooks to support them. Guha's  Documentation and Information,  Prasher's Introduction to Reprography, Vishwanathan's Cataloguing - Theory and Practice and Krishan Kumar's  Theory of Classification  are textbooks on documentation, reprography, cataloguing and classification, respectively, meant for library science students.